Method and apparatus of generating PDMAT precursor

ABSTRACT

A precursor and method for filling a feature in a substrate. The method generally includes depositing a barrier layer, the barrier layer being formed from pentakis(dimethylamido)tantalum having less than about 5 ppm of impurities. The method additionally may include depositing a seed layer over the barrier layer and depositing a conductive layer over the seed layer. The precursor generally includes pentakis(dimethylamido)tantalum having less than about 5 ppm of impurities. The precursor is generated in a canister coupled to a heating element configured to reduce formation of impurities.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/447,255, filed May 27, 2003, which is a continuation-in-part of U.S.patent application Ser. No. 10/198,727, filed Jul. 17, 2002, which areboth incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to depositing a barrier layer ona semiconductor substrate.

2. Description of the Related Art

Reliably producing sub-micron and smaller features is one of the keytechnologies for the next generation of very large scale integration(VLSI) and ultra large scale integration (ULSI) of semiconductordevices. However, as the fringes of circuit technology are pressed, theshrinking dimensions of interconnects in VLSI and ULSI technology haveplaced additional demands on the processing capabilities. The multilevelinterconnects that lie at the heart of this technology require preciseprocessing of high aspect ratio features, such as vias and otherinterconnects. Reliable formation of these interconnects is veryimportant to VLSI and ULSI success and to the continued effort toincrease circuit density and quality of individual substrates.

As circuit densities increase, the widths of vias, contacts and otherfeatures, as well as the dielectric materials between them, decrease tosub-micron dimensions (e.g., less than about 0.20 micrometers or less),whereas the thickness of the dielectric layers remains substantiallyconstant, with the result that the aspect ratios for the features, i.e.,their height divided by width, increase. Many traditional depositionprocesses have difficulty filling sub-micron structures where the aspectratio exceeds 4:1, and particularly where the aspect ratio exceeds 10:1.Therefore, there is a great amount of ongoing effort being directed atthe formation of substantially void-free and seam-free sub-micronfeatures having high aspect ratios.

Currently, copper and its alloys have become the metals of choice forsub-micron interconnect technology because copper has a lowerresistivity than aluminum, (about 1.7 μΩ-cm compared to about 3.1 μΩ-cmfor aluminum), and a higher current carrying capacity and significantlyhigher electromigration resistance. These characteristics are importantfor supporting the higher current densities experienced at high levelsof integration and increased device speed. Further, copper has a goodthermal conductivity and is available in a highly pure state.

Copper metallization can be achieved by a variety of techniques. Atypical method generally includes physical vapor depositing a barrierlayer over a feature, physical vapor depositing a copper seed layer overthe barrier layer, and then electroplating a copper conductive materiallayer over the copper seed layer to fill the feature. Finally, thedeposited layers and the dielectric layers are planarized, such as bychemical mechanical polishing (CMP), to define a conductive interconnectfeature.

However, one problem with the use of copper is that copper diffuses intosilicon, silicon dioxide, and other dielectric materials which maycompromise the integrity of devices. Therefore, conformal barrier layersbecome increasingly important to prevent copper diffusion. Tantalumnitride has been used as a barrier material to prevent the diffusion ofcopper into underlying layers. However, the chemicals used in thebarrier layer deposition, such as pentakis(dimethylamido) tantalum(PDMAT; Ta[NH₂(CH₃)₂]₅), may include impurities that cause defects inthe fabrication of semiconductor devises and reduce process yields.Therefore, there exists a need for a method of depositing a barrierlayer from a high-purity precursor.

SUMMARY OF THE INVENTION

Embodiments of the present invention include a method for filling afeature in a substrate. In one embodiment, the method includesdepositing a barrier layer formed from purifiedpentakis(dimethylamido)tantalum having less than about 5 ppm ofchlorine. The method additionally may include depositing a seed layerover the barrier layer and depositing a conductive layer over the seedlayer.

Embodiments of the present invention further include a canister forvaporizing PDMAT prior to depositing a tantalum nitride layer on asubstrate. The canister includes a sidewall, a top portion and a bottomportion. The canister defines an interior volume having an upper regionand a lower region. A heater surrounds the canister, in which the heatercreates a temperature gradient between the upper region and the lowerregion.

Embodiments of the present invention further include purifiedpentakis(dimethylamido)tantalum having less than about 5 ppm ofchlorine.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention are attained and can be understood in detail, a moreparticular description of the invention, briefly summarized above, maybe had by reference to the embodiments thereof, which are illustrated inthe appended drawings. It is to be noted, however, that the appendeddrawings illustrate only typical embodiments of this invention, and aretherefore, not to be considered limiting of its scope, for the inventionmay admit to other equally effective embodiments.

FIG. 1 is a schematic cross-sectional view of one embodiment of abarrier layer formed over a substrate by atomic layer deposition (ALD).

FIGS. 2A-2C illustrate one embodiment of the alternating chemisorptionof monolayers of a tantalum containing compound and a nitrogencontaining compound on an exemplary portion of substrate.

FIG. 3 is a schematic cross-sectional view of one exemplary embodimentof a processing system that may be used to form one or more barrierlayers by atomic layer deposition.

FIG. 4A is a sectional side view of one embodiment of a gas generationcanister;

FIG. 4B is a sectional top view of the gas generation canister of FIG.4A;

FIG. 5 is a sectional view of another embodiment of a gas generationcanister; and

FIG. 6 is a sectional side view of another embodiment of a gasgeneration canister.

FIG. 7 illustrates a sectional view of a canister surrounded by acanister heater in accordance with one embodiment of the invention.

FIG. 8 illustrates a sectional view of a canister containing a pluralityof solid particles in accordance with one embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a schematic cross-sectional view of one embodiment of asubstrate 100 having a dielectric layer 102 and a barrier layer 104deposited thereon. Depending on the processing stage, the substrate 100may be a silicon semiconductor substrate, or other material layer, whichhas been formed on the substrate. The dielectric layer 102 may be anoxide, a silicon oxide, carbon-silicon-oxide, a fluoro-silicon, a porousdielectric, or other suitable dielectric formed and patterned to providea contact hole or via 102H extending to an exposed surface portion 102Tof the substrate 100. For purposes of clarity, the substrate 100 refersto any work piece upon which film processing is performed, and asubstrate structure 150 is used to denote the substrate 100 as well asother material layers formed on the substrate 100, such as thedielectric layer 102. It is also understood by those with skill in theart that the present invention may be used in a dual damascene processflow. The barrier layer 104 is formed over the substrate structure 150of FIG. 1A by atomic layer deposition (ALD). Preferably, the barrierlayer includes a tantalum nitride layer.

In one aspect, atomic layer deposition of a tantalum nitride barrierlayer includes sequentially providing a tantalum containing compound anda nitrogen-containing compound to a process chamber. Sequentiallyproviding a tantalum containing compound and a nitrogen-containingcompound may result in the alternating chemisorption of monolayers of atantalum-containing compound and of monolayers of a nitrogen-containingcompound on the substrate structure 150.

FIGS. 2A-2C illustrate one embodiment of the alternating chemisorptionof monolayers of a tantalum containing compound and a nitrogencontaining compound on an exemplary portion of substrate 200 in a stageof integrated circuit fabrication, and more particularly at a stage ofbarrier layer formation. In FIG. 2A, a monolayer of a tantalumcontaining compound is chemisorbed on the substrate 200 by introducing apulse of the tantalum containing compound 205 into a process chamber.

The tantalum containing compound 205 typically includes tantalum atoms210 with one or more reactive species 215. In one embodiment, thetantalum containing compound is pentadimethylamino-tantalum (PDMAT;Ta(NMe₂)₅). PDMAT may be used to advantage for a number of reasons.PDMAT is relatively stable. In addition, PDMAT has an adequate vaporpressure which makes it easy to deliver. In particular, PDMAT may beproduced with a low halide content. The halide content of PDMAT shouldbe produced with a halide content of less than 100 ppm. Not wishing tobe bound by theory, it is believed that an organo-metallic precursorwith a low halide content is beneficial because halides (such aschlorine) incorporated in the barrier layer may attack the copper layerdeposited thereover.

Thermal decomposition of the PDMAT during production may causeimpurities in the PDMAT product, which is subsequently used to form thetantalum nitride barrier layer. The impurities may include compoundssuch as CH₃NTa(N(CH₃)₂)₃ and ((CH₃)₂N)₃Ta(NCH₂CH₃). In addition,reactions with moisture may result in tantalum oxo amide compounds inthe PDMAT product. Preferably, the tantalum oxo amide compounds areremoved from the PDMAT by sublimation. For example, the tantalum oxoamide compounds are removed in a bubbler. The PDMAT product preferablyhas less than about 5 ppm of chlorine. In addition, the levels oflithium, iron, fluorine, bromine and iodine should be minimized. Mostpreferably, the total level of impurities is less than about 5 ppm.

The tantalum containing compound may be provided as a gas or may beprovided with the aid of a carrier gas. Examples of carrier gases whichmay be used include, but are not limited to, helium (He), argon (Ar),nitrogen (N₂), and hydrogen (H₂).

After the monolayer of the tantalum containing compound is chemisorbedonto the substrate 200, excess tantalum containing compound is removedfrom the process chamber by introducing a pulse of a purge gas thereto.Examples of purge gases which may be used include, but are not limitedto, helium (He), argon (Ar), nitrogen (N₂), hydrogen (H₂), and othergases.

Referring to FIG. 2B, after the process chamber has been purged, a pulseof a nitrogen containing compound 225 is introduced into the processchamber. The nitrogen containing compound 225 may be provided alone ormay be provided with the aid of a carrier gas. The nitrogen containingcompound 225 may comprise nitrogen atoms 230 with one or more reactivespecies 235. The nitrogen containing compound preferably includesammonia gas (NH₃). Other nitrogen containing compounds may be used whichinclude, but are not limited to, N_(x)H_(y) with x and y being integers(e.g., hydrazine (N₂H₄)), dimethyl hydrazine ((CH₃)₂N2H2),t-butylhydrazine (C₄H₉N₂H₃) phenylhydrazine (C₆H₅N₂H₃), other hydrazinederivatives, a nitrogen plasma source (e.g., N₂, N₂/H₂, NH₃, or a N₂H₄plasma), 2,2′-azoisobutane ((CH₃)₆C₂N₂), ethylazide (C₂H₅N₃), and othersuitable gases. A carrier gas may be used to deliver the nitrogencontaining compound if necessary.

A monolayer of the nitrogen containing compound 225 may be chemisorbedon the monolayer of the tantalum containing compound 205. Thecomposition and structure of precursors on a surface during atomic-layerdeposition (ALD) is not precisely known. Not wishing to be bound bytheory, it is believed that the chemisorbed monolayer of the nitrogencontaining compound 225 reacts with the monolayer of the tantalumcontaining compound 205 to form a tantalum nitride layer 209. Thereactive species 215, 235 form by-products 240 that are transported fromthe substrate surface by the vacuum system.

After the monolayer of the nitrogen containing compound 225 ischemisorbed on the monolayer of the tantalum containing compound, anyexcess nitrogen containing compound is removed from the process chamberby introducing another pulse of the purge gas therein. Thereafter, asshown in FIG. 2C, the tantalum nitride layer deposition sequence ofalternating chemisorption of monolayers of the tantalum containingcompound and of the nitrogen containing compound may be repeated, ifnecessary, until a desired tantalum nitride thickness is achieved.

In FIGS. 2A-2C, the tantalum nitride layer formation is depicted asstarting with the chemisorption of a monolayer of a tantalum containingcompound on the substrate followed by a monolayer of a nitrogencontaining compound. Alternatively, the tantalum nitride layer formationmay start with the chemisorption of a monolayer of a nitrogen containingcompound on the substrate followed by a monolayer of the tantalumcontaining compound. Furthermore, in an alternative embodiment, a pumpevacuation alone between pulses of reactant gases may be used to preventmixing of the reactant gases.

The time duration for each pulse of the tantalum containing compound,the nitrogen containing compound, and the purge gas is variable anddepends on the volume capacity of a deposition chamber employed as wellas a vacuum system coupled thereto. For example, (1) a lower chamberpressure of a gas will require a longer pulse time; (2) a lower gas flowrate will require a longer time for chamber pressure to rise andstabilize requiring a longer pulse time; and (3) a large-volume chamberwill take longer to fill and will take longer for chamber pressure tostabilize thus requiring a longer pulse time. Similarly, time betweeneach pulse is also variable and depends on volume capacity of theprocess chamber as well as the vacuum system coupled thereto. Ingeneral, the time duration of a pulse of the tantalum containingcompound or the nitrogen containing compound should be long enough forchemisorption of a monolayer of the compound. In general, the pulse timeof the purge gas should be long enough to remove the reactionby-products and/or any residual materials remaining in the processchamber.

Generally, a pulse time of about 1.0 second or less for a tantalumcontaining compound and a pulse time of about 1.0 second or less for anitrogen containing compound are typically sufficient to chemisorbalternating monolayers on a substrate. A pulse time of about 1.0 secondor less for a purge gas is typically sufficient to remove reactionby-products as well as any residual materials remaining in the processchamber. Of course, a longer pulse time may be used to ensurechemisorption of the tantalum containing compound and the nitrogencontaining compound and to ensure removal of the reaction by-products.

During atomic layer deposition, the substrate may be maintainedapproximately below a thermal decomposition temperature of a selectedtantalum containing compound. An exemplary heater temperature range tobe used with tantalum containing compounds identified herein isapproximately between about 20° C. and about 500° C. at a chamberpressure less than about 100 torr, preferably less than 50 torr. Whenthe tantalum containing gas is PDMAT, the heater temperature ispreferably between about 100° C. and about 300° C., more preferablybetween about 175° C. and 250° C. In other embodiments, it should beunderstood that other temperatures may be used. For example, atemperature above a thermal decomposition temperature may be used.However, the temperature should be selected so that more than 50 percentof the deposition activity is by chemisorption processes. In anotherexample, a temperature above a thermal decomposition temperature may beused in which the amount of decomposition during each precursordeposition is limited so that the growth mode will be similar to anatomic layer deposition growth mode.

One exemplary process of depositing a tantalum nitride layer by atomiclayer deposition in a process chamber includes sequentially providingpentadimethylamino-tantalum (PDMAT) at a flow rate between about 100sccm and about 1000 sccm, and preferably between about 200 sccm and 500sccm, for a time period of about 1.0 second or less, providing ammoniaat a flow rate between about 100 sccm and about 1000 sccm, preferablybetween about 200 sccm and 500 sccm, for a time period of about 1.0second or less, and a purge gas at a flow rate between about 100 sccmand about 1000 sccm, preferably between about 200 sccm and 500 sccm fora time period of about 1.0 second or less. The heater temperaturepreferably is maintained between about 100° C. and about 300° C. at achamber pressure between about 1.0 and about 5.0 torr. This processprovides a tantalum nitride layer in a thickness between about 0.5 Å andabout 1.0 Å per cycle. The alternating sequence may be repeated until adesired thickness is achieved.

FIG. 3 is a schematic cross-sectional view of one exemplary embodimentof a processing system 320 that may be used to form one or more barrierlayers by atomic layer deposition in accordance with aspects of thepresent invention. Of course, other processing systems may also be used.

The processing system 320 generally includes a processing chamber 306coupled to a gas delivery system 304. The processing chamber 306 may beany suitable processing chamber, for example, those available fromApplied Materials, Inc. located in Santa Clara, Calif. Exemplaryprocessing chambers include DPS CENTURA® etch chambers, PRODUCER®chemical vapor deposition chambers, and ENDURA® physical vapordeposition chambers, among others.

The gas delivery system 304 generally controls the rate and pressure atwhich various process and inert gases are delivered to the processingchamber 306. The number and types of process and other gases deliveredto the processing chamber 306 are generally selected based on theprocess to be performed in the processing chamber 306 coupled thereto.Although for simplicity a single gas delivery circuit is depicted in thegas delivery system 304 shown in FIG. 3, it is contemplated thatadditional gas delivery circuits may be utilized.

The gas delivery system 304 is generally coupled between a carrier gassource 302 and the processing chamber 306. The carrier gas source 302may be a local or remote vessel or a centralized facility source thatsupplies the carrier gas throughout the facility. The carrier gas source302 typically supplies a carrier gas such as argon, nitrogen, helium orother inert or non-reactive gas.

The gas delivery system 304 typically includes a flow controller 310coupled between the carrier gas source 302 and a process gas sourcecanister 300. The flow controller 310 may be a proportional valve,modulating valve, needle valve, regulator, mass flow controller or thelike. One flow controller 310 that may be utilized is available fromSierra Instruments, Inc., located in Monterey, Calif.

The source canister 300 is typically coupled to and located between afirst and a second valve 312, 314. In one embodiment, the first andsecond valves 312, 314 are coupled to the source canister 300 and fittedwith disconnect fittings (not shown) to facilitate removal of the valves312, 314 with the source canister 300 from the gas delivery system 304.A third valve 316 is disposed between the second valve 314 and theprocessing chamber 306 to prevent introduction of contaminates into theprocessing chamber 306 after removal of the source canister 300 from thegas delivery system 304.

FIGS. 4A and 4B depict sectional views of one embodiment of the sourcecanister 300. The source canister 300 generally comprises an ampoule orother sealed container having a housing 420 that is adapted to holdprecursor materials 414 from which a process (or other) gas may begenerated through a sublimation or vaporization process. Some solidprecursor materials 414 that may generate a process gas in the sourcecanister 300 through a sublimation process include xenon difluoride,nickel carbonyl, tungsten hexa-carbonyl, and pentakis (dimethylamino)tantalum (PDMAT), among others. Some liquid precursor materials 414 thatmay generate a process gas in the source canister 300 through avaporization process include tetrakis (dimethylamino) titanium (TDMAT),tertbutyliminotris (diethylamino) tantalum (TBTDET), and pentakis(ethylmethylamino) tantalum (PEMAT), among others. The housing 420 isgenerally fabricated from a material substantially inert to theprecursor materials 414 and gas produced therefrom, and thus, thematerial of construction may vary based on gas being produced.

The housing 420 may have any number of geometric forms. In theembodiment depicted in FIGS. 4A and 4B, the housing 420 comprises acylindrical sidewall 402 and a bottom 432 sealed by a lid 404. The lid404 may be coupled to the sidewall 402 by welding, bonding, adhesives,or other leak-tight method. Alternately, the joint between the sidewall402 and the lid 404 may have a seal, o-ring, gasket, or the like,disposed therebetween to prevent leakage from the source canister 300.The sidewall 402 may alternatively comprise other hollow geometricforms, for example, a hollow square tube.

An inlet port 406 and an outlet port 408 are formed through the sourcecanister to allow gas flow into and out of the source canister 300. Theports 406, 408 may be formed through the lid 404 and/or sidewall 402 ofthe source canister 300. The ports 406, 408 are generally sealable toallow the interior of the source canister 300 to be isolated from thesurrounding environment during removal of the source canister 300 fromthe gas delivery system 304. In one embodiment, valves 312, 314 aresealingly coupled to ports 406, 408 to prevent leakage from the sourcecanister 300 when removed from the gas delivery system 304 (shown inFIG. 3) for recharging of the precursor material 414 or replacement ofthe source canister 300. Mating disconnect fittings 436A, 436B may becoupled to valves 312, 314 to facilitate removal and replacement of thesource canister 300 to and from the gas delivery system 304. Valves 312,314 are typically ball valves or other positive sealing valves thatallows the source canister 300 to be removed from the system efficientlyloaded and recycled while minimizing potential leakage from the sourcecanister 300 during filling, transport, or coupling to the gas deliverysystem 304. Alternatively, the source canister 300 can be refilledthrough a refill port (not shown) such as a small tube with a VCRfitting disposed on the lid 404 of the source canister 300.

The source canister 300 has an interior volume 438 having an upperregion 418 and a lower region 434. The lower region 434 of sourcecanister 300 is at least partially filled with the precursor materials414. Alternately, a liquid 416 may be added to a solid precursormaterial 414 to form a slurry 412. The precursor materials 414, theliquid 416, or the premixed slurry 412 may be introduced into sourcecanister 300 by removing the lid 404 or through one of the ports 406,408. The liquid 416 is selected such that the liquid 416 is non-reactivewith the precursor materials 414, that the precursor materials 414 areinsoluble therein, that the liquid 416 has a negligible vapor pressurecompared to the precursor materials 414, and that the ratio of the vaporpressure of the solid precursor material 414, e.g., tungstenhexa-carbonyl, to that of the liquid 416 is greater than 10³.

Precursor materials 414 mixed with the liquid 416 may be sporadicallyagitated to keep the precursor materials 414 suspended in the liquid 416in the slurry 412. In one embodiment, precursor materials 414 and theliquid 416 are agitated by a magnetic stirrer 440. The magnetic stirrer440 includes a magnetic motor 442 disposed beneath the bottom 432 of thesource canister 300 and a magnetic pill 444 disposed in the lower region434 of the source canister 300. The magnetic motor 442 operates torotate the magnetic pill 444 within the source canister 300, therebymixing the slurry 412. The magnetic pill 444 should have an outercoating of material that is a non-reactive with the precursor materials414, the liquid 416, or the source canister 300. Suitable magneticmixers are commercially available. One example of a suitable magneticmixer is IKAMAG® REO available from IKA® Works in Wilmington, NorthCarolina. Alternatively, the slurry 412 may be agitated other means,such as by a mixer, a bubbler, or the like.

The agitation of the liquid 416 may induce droplets of the liquid 416 tobecome entrained in the carrier gas and carried toward the processingchamber 306. To prevent such droplets of liquid 416 from reaching theprocessing chamber 306, an oil trap 450 may optionally be coupled to theexit port 408 of the source canister 300. The oil trap 450 includes abody 452 containing a plurality of interleaved baffles 454 which extendpast a centerline 456 of the oil trap body 452 and are angled at leastslightly downward towards the source canister 300. The baffles 454 forcethe gas flowing towards the processing chamber 306 to flow a tortuouspath around the baffles 454. The surface area of the baffles 454provides a large surface area exposed to the flowing gas to which oildroplets that may be entrained in the gas adhere. The downward angle ofthe baffles 454 allows any oil accumulated in the oil trap to flowdownward and back into the source canister 300.

The source canister 300 includes at least one baffle 410 disposed withinthe upper region 418 of the source canister 300. The baffle 410 isdisposed between inlet port 406 and outlet port 408, creating anextended mean flow path, thereby preventing direct (i.e., straight line)flow of the carrier gas from the inlet port 406 to the outlet port 408.This has the effect of increasing the mean dwell time of the carrier gasin the source canister 300 and increasing the quantity of sublimated orvaporized precursor gas carried by the carrier gas. Additionally, thebaffles 410 direct the carrier gas over the entire exposed surface ofthe precursor material 414 disposed in the source canister 300, ensuringrepeatable gas generation characteristics and efficient consumption ofthe precursor materials 414.

The number, spacing and shape of the baffles 410 may be selected to tunethe source canister 300 for optimum generation of precursor gas. Forexample, a greater number of baffles 410 may be selected to imparthigher carrier gas velocities at the precursor material 414 or the shapeof the baffles 410 may be configured to control the consumption of theprecursor material 414 for more efficient usage of the precursormaterial.

The baffle 410 may be attached to the sidewall 402 or the lid 404, orthe baffle 410 may be a prefabricated insert designed to fit within thesource canister 300. In one embodiment, the baffles 410 disposed in thesource canister 300 comprise five rectangular plates fabricated of thesame material as the sidewall 402. Referring to FIG. 4B, the baffles 410are welded or otherwise fastened to the sidewall 402 parallel to eachother. The baffles 410 are interleaved, fastened to opposing sides ofthe source canister in an alternating fashion, such that a serpentineextended mean flow path is created. Furthermore, the baffles 410 aresituated between the inlet port 406 and the outlet port 408 on the lid404 when placed on the sidewall 402 and are disposed such that there isno air space between the baffles 410 and the lid 404. The baffles 410additionally extend at least partially into the lower region 434 of thesource canister 300, thus defining an extended mean flow path for thecarrier gas flowing through the upper region 418.

Optionally, an inlet tube 422 may be disposed in the interior volume 438of the source canister 300. The tube 422 is coupled by a first end 424to the inlet port 406 of the source canister 300 and terminates at asecond end 426 in the upper region 418 of the source canister 300. Thetube 422 injects the carrier gas into the upper region 418 of the sourcecanister 300 at a location closer to the precursor materials 414 or theslurry 412.

The precursor materials 414 generate a precursor gas at a predefinedtemperature and pressure. Sublimating or vaporized gas from theprecursor materials 414 accumulate in the upper region 418 of the sourcecanister 300 and are swept out by an inert carrier gas entering throughinlet port 406 and exiting outlet port 408 to be carried to theprocessing chamber 306. In one embodiment, the precursor materials 414are heated to a predefined temperature by a resistive heater 430disposed proximate to the sidewall 402. Alternately, the precursormaterials 414 may be heated by other means, such as by a cartridgeheater (not shown) disposed in the upper region 418 or the lower region434 of the source canister 300 or by preheating the carrier gas with aheater (not shown) placed upstream of the carrier gas inlet port 406. Tomaximize uniform heat distribution throughout the slurry 412, the liquid416 and the baffles 410 should be good conductors of heat.

In accordance with yet another embodiment of the invention, a pluralityof solid beads or particles 810 with high thermal conductivity, such as,aluminum nitride or boron nitride, may be used in lieu of the liquid416, as shown in FIG. 8. Such solid particles 810 may be used totransfer more heat from the sidewall of the canister 800 to theprecursor materials 414 than the liquid 416. The solid particles 810have the same properties as the liquid 416 in that they are non-reactivewith the precursor materials 414, insoluble, have a negligible vaporpressure compared to the precursor materials 414. As such, the solidparticles 810 are configured to efficiently transfer heat from thesidewall of the canister 800 to the center portion of the canister 800,thereby leading to more precursor material utilization duringsublimation or vaporization. The solid particles 810 may also bedegassed and cleaned from contaminants, water vapor and the like, priorto being deposited into the canister 800.

In one exemplary mode of operation, the lower region 434 of the sourcecanister 300 is at least partially filled with a mixture of tungstenhexa-carbonyl and diffusion pump oil to form the slurry 412. The slurry412 is held at a pressure of about 5 Torr and is heated to a temperaturein the range of about 40 degrees Celsius to about 50 degrees Celsius bya resistive heater 430 located proximate to the source canister 300.Carrier gas in the form of argon is flowed through inlet port 406 intothe upper region 418 at a rate of about 400 standard cc/min. The argonflows in an extended mean flow path defined by the torturous paththrough the baffles 410 before exiting the source canister 300 throughoutlet port 408, advantageously increasing the mean dwell time of theargon in the upper region 418 of the source canister 300. The increaseddwell time in the source canister 300 advantageously increases thesaturation level of sublimated tungsten hexa-carbonyl vapors within thecarrier gas. Moreover, the torturous path through the baffles 410advantageously exposes the substantially all of the exposed surface areaof the precursor material 414 to the carrier gas flow for uniformconsumption of the precursor material 414 and generation of theprecursor gas.

FIG. 7 illustrates another embodiment for heating the precursormaterials 414. More specifically, FIG. 7 illustrates a sectional view ofa canister 700 surrounded by a canister heater 730, which is configuredto create a temperature gradient between a lower region 434 of thecanister 700 and an upper region 418 of the canister 700 with the lowerregion 434 being the coldest region and the upper region 418 being thehottest region. The temperature gradient may range from about 5 degreesCelsius to about 15 degrees Celsius. Since solid precursor materialsgenerally tend to accumulate or condense at the coldest region of thecanister 700, the canister heater 730 is configured to ensure that thesolid precursor materials 414 will accumulate at the lower region 434 ofthe canister 700, thereby increasing the predictability of where thesolid precursor materials 414 will condense and the temperature of thesolid precursor materials 414. The canister heater 730 includes aheating element 750 disposed inside the canister heater 730 such thatthe entire canister 700, including the upper region 418 and the lowerregion 434, is heated by the canister heater 730. The heating element750 near the upper region 418 may be configured to generate more heatthan the heating element 750 near the lower region 434, thereby allowingthe canister heater 730 to create the temperature gradient between thelower region 434 and the upper region 418. In one embodiment, theheating element 750 is configured such that the temperature at the upperregion 418 is between about 5 degrees to about 15 degrees Celsius higherthan the temperature at the lower region 434. In another embodiment, theheating element 750 is configured such that the temperature at the upperregion 418 is about 70 degrees Celsius, the temperature at the lowerregion 434 is about 60 degrees Celsius and the temperature at thesidewall of the canister 700 is about 65 degrees Celsius. The power ofthe heating element 730 may be about 600 Watts at 208 VAC input.

The canister heater 730 may also include a cooling plate positioned atthe bottom of the canister heater 730 to further ensure that the coldestregion of the canister 700 is the lower region 434, and thereby ensuringthat the solid precursor materials 414 condense at the lower region 434.Further, the valves 312, 314, the oil trap 450, the inlet port 406 andthe exit port 408 may be heated with a resistive heating tape. Since theupper region 418 is configured to have a higher temperature than thelower region 434, the baffles 410 may be used to transfer heat from theupper region 418 to the lower region 434, thereby allowing the canisterheater 730 to maintain the desired temperature gradient. Embodiments ofthe invention also contemplate other heat transfer medium, such as,silos (not shown) extending from the bottom portion 432 of the canister700 to the upper region 418.

FIG. 5 depicts a sectional view of another embodiment of a canister 500for generating a process gas. The canister 500 includes a sidewall 402,a lid 404 and a bottom 432 enclosing an interior volume 438. At leastone of the lid 404 or sidewall 402 contains an inlet port 406 and anoutlet port 408 for gas entry and egress. The interior volume 438 of thecanister 500 is split into an upper region 418 and a lower region 434.Precursor materials 414 at least partially fill the lower region 434.The precursor materials 414 may be in the form of a solid, liquid orslurry, and are adapted to generate a process gas by sublimation and/orvaporization.

A tube 502 is disposed in the interior volume 438 of the canister 500and is adapted to direct a flow of gas within the canister 500 away fromthe precursor materials 414, advantageously preventing gas flowing outof the tube 502 from directly impinging the precursor materials 414 andcausing particulates to become airborne and carried through the outletport 408 and into the processing chamber 306. The tube 502 is coupled ata first end 504 to the inlet port 406. The tube 502 extends from thefirst end 504 to a second end 526A that is positioned in the upperregion 418 above the precursor materials 414. The second end 526A may beadapted to direct the flow of gas toward the sidewall 402, thuspreventing direct (linear or line of sight) flow of the gas through thecanister 500 between the ports 406, 408, creating an extended mean flowpath.

In one embodiment, an outlet 506 of the second end 526A of the tube 502is oriented an angle of about 15 to about 90 degrees relative to acenter axis 508 of the canister 500. In another embodiment, the tube 502has a ‘J’-shaped second end 526B that directs the flow of gas exitingthe outlet 506 towards the lid 404 of the canister 500. In anotherembodiment, the tube 502 has a capped second end 526C having a plug orcap 510 closing the end of the tube 502. The capped second end 526C hasat least one opening 528 formed in the side of the tube 502 proximatethe cap 510. Gas, exiting the openings 528, is typically directedperpendicular to the center axis 508 and away from the precursormaterials 414 disposed in the lower region 434 of the canister 500.Optionally, at least one baffle 410 (shown in phantom) as describedabove may be disposed within the chamber 500 and utilized in tandem withany of the embodiments of the tube 502 described above.

In one exemplary mode of operation, the lower region 434 of the canister500 is at least partially filled with a mixture of tungstenhexa-carbonyl and diffusion pump oil to form the slurry 412. The slurry412 is held at a pressure of about 5 Torr and is heated to a temperaturein the range of about 40 to about 50 degrees Celsius by a resistiveheater 430 located proximate to the canister 500. A carrier gas in theform of argon is flowed through the inlet port 406 and the tube 502 intothe upper region 418 at a rate of about 200 standard cc/min. The secondend 526A of the tube 502 directs the flow of the carrier gas in anextended mean flow path away from the outlet port 408, advantageouslyincreasing the mean dwell time of the argon in the upper region 418 ofthe canister 500 and preventing direct flow of carrier gas upon theprecursor materials 414 to minimize particulate generation. Theincreased dwell time in the canister 500 advantageously increases thesaturation level of sublimated tungsten hexa-carbonyl gas within thecarrier gas while the decrease in particulate generation improvesproduct yields, conserves source solids, and reduces downstreamcontamination.

FIG. 6 depicts a sectional view of another embodiment of a canister 600for generating a precursor gas. The canister 600 includes a sidewall402, a lid 404 and a bottom 432 enclosing an interior volume 438. Atleast one of the lid 404 or sidewall 402 contains an inlet port 406 andan outlet port 408 for gas entry and egress. Inlet and outlet ports 406,408 are coupled to valves 312, 314 fitted with mating disconnectfittings 436A, 436B to facilitate removal of the canister 600 from thegas delivery system 304. Optionally, an oil trap 450 is coupled betweenthe outlet port 408 and the valve 314 to capture any oil particulatethat may be present in the gas flowing to the process chamber 306.

The interior volume 438 of the canister 600 is split into an upperregion 418 and a lower region 434. Precursor materials 414 and a liquid416 at least partially fill the lower region 434. A tube 602 is disposedin the interior volume 438 of the canister 600 and is adapted to directa first gas flow F₁ within the canister 600 away from the precursormaterial and liquid mixture and to direct a second gas flow F₂ throughthe mixture. The flow F₁ is much greater than the flow F₂. The flow F₂is configured to act as a bubbler, being great enough to agitate theprecursor material and liquid mixture but not enough to cause particlesor droplets of the precursor materials 414 or liquid 416 from becomingairborne. Thus, this embodiment advantageously agitates the precursormaterial and liquid mixture while minimizing particulates produced dueto direct impingement of the gas flowing out of the tube 602 on theprecursor materials 414 from becoming airborne and carried through theoutlet port 408 and into the processing chamber 306.

The tube 602 is coupled at a first end 604 to the inlet port 406. Thetube 602 extends from the first end 604 to a second end 606 that ispositioned in the lower region 434 of the canister 600, within theprecursor material and liquid mixture. The tube 602 has an opening 608disposed in the upper region 418 of the canister 600 that directs thefirst gas flow F₁ towards a sidewall 402 of the canister 600. The tube600 has a restriction 610 disposed in the upper region 438 of thecanister 600 located below the opening 608. The restriction 610 servesto decrease the second gas flow F₂ flowing toward the second end 606 ofthe tube 602 and into the slurry 412. By adjusting the amount of therestriction, the relative rates of the first and second gas flows F₁ andF₂ can be regulated. This regulation serves at least two purposes.First, the second gas flow F₂ can be minimized to provide just enoughagitation to maintain suspension or mixing of the precursor materials414 in the liquid 416 while minimizing particulate generation andpotential contamination of the processing chamber 306. Second, the firstgas flow F₁ can be regulated to maintain the overall flow volumenecessary to provide the required quantity of sublimated and/or vaporsfrom the precursor materials 414 to the processing chamber 306.

Optionally, an at least one baffle 410 as described above may bedisposed within the canister 600 and utilized in tandem with any of theembodiments of the tube 602 described above.

While foregoing is directed to the preferred embodiment of the presentinvention, other and further embodiments of the invention may be devisedwithout departing from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. Apparatus for generating a precursor for a semiconductor processingsystem, comprising: a canister having a sidewall, a top and a bottomdefining an interior volume; an inlet port and an outlet port incommunication with the interior volume; a plurality of baffles withinthe interior volume; and a heater coupled to the canister, wherein theplurality of baffles define an extended mean flow path between the inletport and the outlet port.
 2. The apparatus of claim 1, wherein theplurality of baffles are coupled to the top.
 3. The apparatus of claim1, wherein the plurality of baffles are coupled to the sidewall.
 4. Theapparatus of claim 1, wherein the heater is disposed proximate thesidewall of the canister.
 5. The apparatus of claim 1, wherein theheater is disposed proximate the sidewall, the top, and the bottom ofthe canister.
 6. The apparatus of claim 1, further comprising a coolingplate disposed proximate the bottom of the canister.
 7. The apparatus ofclaim 1, wherein the canister comprises a heat transfer medium withinthe interior volume.
 8. The apparatus of claim 7, wherein the heattransfer medium is at least one of the plurality of baffles.
 9. Theapparatus of claim 7, wherein the heat transfer medium is a plurality ofsolid particles at least partially filling the interior volume.
 10. Theapparatus of claim 9, wherein the plurality of solid particles areselected from; aluminum nitride, boron nitride, or combinations thereof.11. The apparatus of claim 7, wherein the heat transfer medium is aliquid.
 12. The apparatus of claim 1, further comprising: a precursormaterial at least partially filling the canister.
 13. The apparatus ofclaim 12, wherein the precursor material is pentadimethylamino-tantalumhaving less than 5 ppm impurities.
 14. The apparatus of claim 1, furthercomprising: an oil trap coupled to the outlet port.
 15. Apparatus forgenerating a precursor for a semiconductor processing system,comprising: a canister defining an interior volume; a precursor materialand a plurality of solid particles at least partially filling theinterior volume; and a heater coupled to the canister, wherein theplurality of solid particles are in communication with the heater andthe precursor material.
 16. The apparatus of claim 15, wherein theprecursor material is pentadimethylamino-tantalum having less than 5 ppmimpurities.
 17. The apparatus of claim 15, wherein the canister furthercomprises: a top, a bottom, and sidewalls; an inlet port and an outletport in communication with the interior volume; an oil trap coupled tothe outlet port; and a plurality of baffles within the interior region.18. The apparatus of claim 17, wherein the baffles are coupled to thetop of the canister.
 19. The apparatus of claim 17, wherein the bafflesare coupled to the sidewall of the canister.
 20. The apparatus of claim17, wherein the inlet port further comprises an inlet tube adapted todirect the flow of a carrier gas away from the precursor material andthe plurality of solid particles.